Angular: why isn't $evalAsync called $applyAsync?
angularjs, angularjs-digest, asynchronous, definition
Solution
`$evalAsync` and `$applyAsync` target to different situations.
$evalAsync: defers the expression to the next loop iteration of current digest cycle. One Angular digest cycle loops for a few times until no data is dirty. If no digest cycle is in progress, it will start a new digest cycle (call `$apply` method) and evaluate the expression (call `$eval` method) in it. This method is useful if you call a function out of Angular scope but still like to digest the dirty data when a digest cycle is already in progress, in which case you cannot call `$apply`.
$applyAsync: defers the expression to the next cycle of digest. It always starts a new cycle of digest to after the expression is evaluated (call `$apply` method). This method is useful if you frequently execute some service call back (like `$http` service) out Angular scope with dirty scope data. However, if it starts a digest for each callback, there may be bad performance. Therefore, this method optimize the process by share the digest cycles among several async callbacks, which outperforms the method `$evalAsync`.
Problem
Angular beginner question about scopes (docs here). - `$eval` executes an expression in the context of a scope. - `$apply` basically calls `$eval` and then `$digest`. - Why does `$evalAsync` call `$digest` too (or, more precisely, ensure `$digest` is called)? It seems to be that `$``eval``Async` should really be called `$``apply``Async`, doesn't it? I'm a beginner -- what am I missing?